Rubber modified asphalt compositions as defined in U.S. Pat. No. 4,273,685 to Marzocchi et al., the disclosure of which is incorporated herein by reference, are a recent invention. Succinctly, these compositions comprise a chemically-modified asphalt which has been reacted with a polymerizable vinyl aromatic monomer and a rubbery polymer, the reaction having been carried out at a temperature at which the vinyl aromatic monomer and the rubbery polymer react with the asphalt. The rubbery polymer can be selected from the group consisting of homo-polymers of a conjugated dienes and copolymers formed of a conjugated diene and at least one ethylenic monomer copolymerizable therewith.
The ethylenic monomer is selected from the group consisting of styrene, acrylonitrile, methacrylonitrile, acrylic acid, methacrylic acid, hydroystrene, aminostryene mercaptostyrene, and vinyl toluene.
Relatedly, there have recently been developed solvent solutions of these chemically modified asphalts. Two types of these have been developed.
The first of these is a homogenous, stable solution of the reaction product of asphalt, a vinyl aromatic monomer, and a rubbery polymer in an organic solvent, the solvent being selected from the group consisting of (a) toluene, (b) a mixture of toluene and xylene having a minimum of about 25 percent by weight toluene and a maximum of about 75 percent by weight xylene, (c) a mixture of toluene and Stoddard solvent having a minimum of about 40 percent toluene and a maximum of about 60 percent Stoddard solvent, (d) a mixture of toluene, xylene and at least one compound selected from the group consisting of heptane and hexane, the mixture having a minimum of about 25 percent toluene, a maximum of about 55 percent xylene and a maximum of about 20 percent of heptane or hexane or a mixture thereof, (e) a mixture of toluene, Stoddard solvent and heptane or hexane, or a mixture of heptane or hexane, the maximum amount of heptane or hexane, or a mixture thereof, being about 25 percent, the minimum amount of toluene being about 40 percent and the maximum amount of Stoddard solvent being about 55 percent, all percentages being weight percent and (f) a mixture of from about 40 to about 90 percent toluene and from about 10 to about 60 percent hexane or heptane.
All solutions are simply prepared by combining the chemically modified asphalt and the above defined solvents with agitation being applied for a sufficient period of time to form a homogenous solution.
The second of the solvent solutions of the chemically modified asphalts comprises a homogenous, stable organic solvent solution of the reaction product of asphalt, a polymerizable vinyl aromatic monomer, and a rubbery polymer, the solvent being selected from the group consisting of (a) a mixture consisting essentially of about 40 to about 80 weight percent xylene and about 20 to about 60 weight percent Stoddard solvent and (b) a mixture consisting essentially of xylene, Stoddard solvent and hexane or heptane, or a mixture of hexane and heptane, with xylene being present in an amount of about 40 to about 80 weight percent, the Stoddard solvent being present in an amount of about 5 to about 35 weight percent, the hexane or heptane, or mixture thereof, being present in a maximum amount of about 25 weight percent.